THIEVES have taken the shine off the Ninth International Jewellery Show by making off with a big haul for the second time in three days. A gang yesterday stole 200 diamond and pearl rings worth $300,000. Lacklustre security was blamed for the first theft on Wednesday and was upgraded, but police said it was still not good enough. Three European men and a European woman were the suspects who made a mockery of metal detectors, security searches and electronic eyes at Wan Chai's Convention and Exhibition Centre. The theft from a Sunny Creations booth led police to berate organisers and accuse exhibitors of carelessness. A spokesman for the Crime Prevention Bureau denied organisers' claims that all security guidelines had been followed. ''For them to say they have followed all guidelines is simply not true. For a start, there are too many entry and exit points. ''We wanted more restrictions on movement and we also wanted stronger display cabinets with better locks,'' he said. ''Exhibitors are just not equipped to handle responsibility for expensive goods. The place could be secured like a fortress but if people are just going to leave jewels unattended they are likely to get stolen.'' Yesterday's theft followed the loss of 83 diamond rings worth $500,000. Hong Kong Trade Development Council manager William Cheung Chee-fai said organisers followed all security guidelines. ''Security at the show is our main concern. We're reviewing it every day,'' he said.